1. Technical Field of the Invention
The present invention relates to a device for conducting a biochemical assay and, in particular, to such a device configured for optical scanning of biochemical sensor wells in a testing assay plate.
2. Description of Related Art
Biomedical assaying techniques are well known in the art. Fluorescence comprises one well known transduction method. In this technique, a biological material sample (such as blood, feces, urine, and the like) under examination undergoes a biochemical reaction at a biochemical sensor well. This chemical reaction generally involves applying one or more reagents to the deposited biological material sample. The reagent(s) is (are) selectively chosen based on a known reaction with a component (for example, a protein) of interest that may or may not be present in the biological material sample to produce a chemical analyte having fluorescing properties. Furthermore, the amount of analyte produced by the chemical reaction is typically proportional to the amount of the component of interest that is present in the deposited sample. The biochemical sensor well is then exposed to light having a known and controlled wavelength and intensity for exciting the analyte, and the resulting fluorescent light emitted by the excited analyte is measured to obtain information indicative of the amount of analyte produced by the chemical reaction. From this information a deduction may be made concerning the amount of the included component of interest contained within the sample.
Complex biochemical assays are preferably performed in an array format wherein a plurality of biochemical sensor wells (also referred to as xe2x80x9ctest cellsxe2x80x9d) are arranged on an assay plate in an nxc3x97m format to allow for the simultaneous testing of plural samples and control groups. An assay reading device is then used to optically scan each of the individual biochemical sensor wells. This scanning operation generally involves the use of a robotic device that moves an ultraviolet illumination device and fluorescent reading device about the plate array from well to well to individually measure emitted fluorescence. From these measurements, a determination may be made of the amount of chemical analyte that is present. This information is then used to obtain an indication of the presence of and the amount of the component of interest that is contained in the sample.
The robotic assay scanning devices known in the art typically include a number of moving parts relating to the illumination device and to the reading device. These moving components are highly susceptible to wear and breakdown. The robotic nature of these devices further significantly adds to the cost of device production and maintenance. These devices can also be quite large in size, and are not easily modified into the compact, smaller form factors that are required for portability. Still further, these robotic devices often inefficiently utilize physically separate illumination and detection components.
What is needed is a biochemical assay device utilizing no moving parts that is suitable for implementation in a very compact form factor. There would also be an advantage if the device utilized a common, perhaps integrated, optical source/detector.
The present invention concerns an imaging system that utilizes an optical waveguide for scanning. A scanning light beam propagates through the optical waveguide by total internal reflection. A refractive index modulator is positioned adjacent waveguide and includes a plurality of optical doors. Each optical door is selectively configurable into either a first refractive condition or a second refractive condition. In the first refractive condition, the optical door has a first index of refraction that continues total internal reflection of the scanning beam. In the second refractive condition, the optical door has a second index of refraction which frustrates total internal reflection and allows the scanning light beam to exit the optical waveguide through the optical door. The exiting scanning light beam is used to illuminate a scanned object with an incident beam of light. The scanned object responds to illumination by generating an emission beam of light that is detected by a photoreceptor.
Embodiments of the present invention still further comprise a biochemical assay device that optically scans individual biological sample containing wells in an assay plate. The device includes an imaging system overlaying the assay plate wherein a scanning light propagates by total internal reflection within an optical waveguide. The waveguide includes a plurality of pixel locations, each aligned with a well in the assay plate, at which total internal reflection is selectively frustrated to output an incident beam of light. The incident beam of light illuminates the well causing generation of an emission beam of light that is received at the pixel location and propagated in the waveguide. A photoreceptor detects the emission beam of light from each illuminated well. The device further includes a driver circuit that controls the selective frustration of total internal reflection at each pixel location in order to scan each well in the assay plate with an incident beam of light. A processor is also included in the device to process the detected emission beams of light generated by the scanned wells for purposes of assaying the biological sample contained in each scanned well.
Embodiments of the present invention still further comprise a method for optically scanning individual wells in an assay plate. A light propagating substrate is positioned overlaying the assay plate. The substrate includes a plurality of pixel locations, with each pixel location being aligned with a well in the assay plate. A scanning light then propagates within the light propagating substrate by total internal reflection. The total internal reflection of the scanning light is then selectively frustrated at each pixel location to output from the light propagating substrate an incident beam of light at each pixel location that illuminates each of the wells in the assay plate. Responsive to the incident beam of light, each illuminated well generates an emission beam of light that is detected.